well, when welder (such as Miller) only works as master, robot must be slave. as a result of this, you cannot use DeviceNet on MFC card of your KRC2 and you need to buy LPDN card. MFC has simple implementation of DeviceNet with few restrictions (can only work as master, does not support coupling, master node address cannot be changed) but - it is free and for most uses it is perfect. LPDN card is a fancy card wit hall bells and whistles, can be master slave or both, supports coupling etc.
in case of KRC4, DeviceNet is added through Kuka Expansion Bus (X44 and EL1100 needed) which typically includes both EL6752 (master) and EL6752-0010 (slave) modules but you can of course only add what you need. Either way prepare for some wiring gymnastics if you have no MultiTap module.
